Cardiac Diseases in Cats and Dogs

Listed below are several of the more prevalent cardiac diseases of cats and dogs.  This is article is intended to be used as a summary of some of the common cardiac diseases.  The article was not written by a cardiologist and is for general knowledge only. Please consult with your veterinarian for any cardiac conditions diagnosed.

The heart is a muscular organ consisting of four chambers- a right and left atrium and right and left ventricles(canine heart, feline heart).  Valves are located between the atrium ,ventricles, and the two major vessels leading to the heart to prevent blood from flowing abnormally.  Blood is circulated through the body by the pumping action of the heart.  Deviations in the size of the chambers, or strength or elasticity of the muscle, or disease of the valves, will affect the flow of blood in the body and subsequently the dynamics of all the organs in the body.  Once the heart begins to malfunction a vicious cycle develops and abnormal fluid build-up begins in different areas of the body depending on which side and part of the heart are involved.  Thus, congestive heart failure develops.  Listed below are several common heart diseases of both cats and dogs.

Cardiomyopathy in cats

Dilated Cardiomyopathy: (Feline Dilated Cardiomyopathy)

Dilated cardiomyopathy is a disease of the ventricular muscle, characterized by a loss of muscle tone of the heart. The heart loses its strength and tone and becomes enlarged, filled with blood and unable to contract properly. Before the mid 1980’s this was one of the most commonly diagnosed heart diseases of cats.  Most cats probably had secondary cardiomyopathy as a result of taurine deficiency.  Due to changes in diet formulation, this is now an uncommon cause of heart disease in cats.  There may also be a genetic component in Siamese, Abyssinian, and Burmese cats.

Clinical signs are related to low cardiac output: loss of appetite, weakness, depression, difficulty breathing, and thromboemboli causing painful paralysis.

Diagnosis is made by x-ray and ultrasound.  Ultrasound is the definitive diagnostic tool.

Treatment is that of congestive heart failure, with the use of digoxin, diuretics such as furosamide, and supplementation of taurine.  Prognosis is poor despite intensive therapy.

Hypertrophic cardiomyopathy: (Hypertrophic Cardiomyopathy)

Hypertrophic cardiomyopathy is a thickening of the heart muscles causing a decrease in the size of the chambers of the heart.  As a result, the heart cannot supply the body the amount of blood it needs due to the decreased volume of blood in the chambers.  Hypertension develops and pulmonary edema (fluid in the lungs) develop. Congestive heart failure, thromboemboli, and abnormal heartbeats (arrythmias) develop.

Clinical signs include difficulty breathing, loss of appetite, exercise intolerance, vomiting, collapse, or sudden death, .  In the early stages the physical exam is normal.  We have observed sudden death in some kittens and cats during routine anesthetic induction.  Post mortum exam reveals cardiomyopathy as the cause of death.  This is similar to the sudden death seen in some young athletes.

Physical signs seen during exams in cats with more developed cardiomyopathy include an abnormal heart- beat, murmur, muffled heart sounds, rapid heart sounds, difficulty breathing, weakened pulses, and early stages of hypertension.

Differential diagnosis includes that of hyperthyroidism, valvular disease, hypertension, trauma, feline asthma, and cancer of the chest.

Diagnosis is based upon x-ray and, most importantly, ultrasound.

Treatment is palliative. In people, heart transplant is the treatment of choice.  In cats, we treat with low sodium diets, medications to treat congestive heart failure such as diltiazem, or atenelol, and aspirin to prevent blood clots. Diuretics may also be used. Low salt diets may be used, but palability may be an issue.  The prognosis varies from good to poor depending upon the severity of the disease.

Restrictive cardiomyopathy of cats:

This is a poorly defined heart disease involving selected areas of the ventricles of the heart.  Scarring of the heart muscle results in both contraction and relaxation difficulties of the heart leading to congestive heart failure.  Cats with restrictive cardiomyopathy have clinical and functional signs similar to both of the other forms of cardiomyopathy.  Dilatation of all cardiac chambers may be evident.

Signs are those of congestive heart failure-poor appetite, weight loss, difficulty breathing, blood clots and paralysis of the limbs.

Differential diagnosis is that of hypertrophic cardiomyopathy, dilated cardiomyopathy, hyperthyroidism and hypertension .

Diagnosis is confirmed by xray-disproportionate atrial enlargement, abnormal lung shadows, and ultrasound. Ultrasound might show an abnormal right atrial enlargement and other changes too complex to discuss on this handout.

Treatment includes diuretics, nitroglycerine application, calcium channel blockers,such as diltiziam, and possible use of beta blockers, such as atenelol.  The diuretic furosamide may also be recommended as well as low dose aspirin.  Low salt diets are recommended, but as stated above palatability may be an issue.

Most cats with restrictive cardiomyopathy live for 3-12 mos.

Cardiomyopathy in dogs

Dilated cardiomyopathy:(Canine Dilated Cardiomyopathy )

This is a flaccidity of the heart muscle similar to cats.  The heart cannot pump properly causing congestive heart failure.  There is a suspicion that this may be a genetic disease.  We see a breed predilection in the Doberman pincher, boxer, giant breeds i.e. Irish wolf hound, Scottish deer hound, great dane.  We also see a taurine related dilated cardiomyopathy in cocker spaniels.

Clinical signs are difficulty breathing, weakness, coughing, weight loss, abdominal distension, fainting, and sudden death.

Exam findings include decreased pulses, abnormal heart sounds and beats, muffled heart sounds, murmurs.

Diagnosis is based upon x-ray and ultrasound.

Treatment for congestive heart failure include treating with ACE inhibitors, such as enalapril, digoxin, and the diuretic furosamide and low salt diets.  Evidence suggests that the nutriceutical supplements taurine and carnatine as well as Co enzyme Q 10 may be of help.

The prognosis is poor.

In our practice we recommend that all American cocker spaniels be placed on taurine as puppies and continued for life.

Hypertrophic cardiomyopathy of dogs:

This is a rare disease of dogs caused by a thickening of the heart musculature.  Due to the thickening of the heart muscle, the size of the heart chamber is smaller resulting in decreased ability of the heart to pump blood to the rest of the body.

This disease has been described in dogs of all ages.

Signs range from asymptomatic to those of congestive heart failure, including heart murmur, difficulty breathing, coughing, and exercise intolerance

Diagnosis is best made with x-ray and ultrasound

Treatment includes rest, low salt diets, diuretics such as furosamide, beta blockers such as atenalol or propanolol or calcium channel blockers such as diltiziam.  People with hypertrophic cardiomyopathy improved symptomatically when given verapmil on a long term basis.  Low salt diets may be recommended.

The prognosis is poor.

Valvular diseases

The heart contains four valves:

- mitral valve (left AV)- the valve between the left atrium and left ventricle - tricuspid valve (right AV)- the valve between the right atrium and right ventricle - aortic or left semilunar valve-the valve between the left ventricle and aortic valve - pulmonic or right semilunar valve-the valve between right ventricle and the pulmonary artery

Valve dysfunction occurs by either congenital or acquired heart disease.  The clinical finding of valvular disease is a cardiac murmur.

Types of valvular disease: (Valvular Disease)

Endocardosis- This is a degenerative disorder and occurs most frequently in dogs and usually involves the mitral valve.  Congenital Aortic Stenosis- Congenital pulmonic valve stenosis, Bacterial endocarditis, Valvular disease due to cardiomyopathy

Diagnosis is made by clinical signs, auscultation (listening to the heart), xray, ultrasound as the definitive diagnostic tool.

Treatment is based on the type and severity of the valvular disease.  Currently, treatment of asymptomatic dogs is not recommended unless changes of the heart size are observed on x-ray.

As the severity of the disease progresses, diuretics, low sodium diets, digoxin, and vasodilator therapy is begun. In most cases the vasodilator can be an ACE (angiotension-converting enzyme) inhibitor.  Furosamide is usually the diuretic first administered.  The use of digoxin in dogs with valvular disease is somewhat controversial.  Most cardiologists now advocate its use in mild cases of heart failure.  It is most definitely used if arrhythmias (abnormal heart beats) are present and if advanced heart failure is present.

There are many other vasodilators available for use such as hydralizine, prazosin, and diltiazem to name a few.  Your veterinarian will prescribe the medication and regimen they are most familiar with.

Pericardial Diseases and Cardiac Cancer:

The pericardium is a sac that surrounds the heart and serves to protect the heart and major vessels.  When diseased it can cause life-threatening restriction of the ventricles.

Pericardial effusion (fluid in the sac) is the most common type of pericardial disease.  This may result from infection, congestive heart failure, hemorrhage due to trauma or cardiac rupture, or cancer.

Clinical signs may be absent and only detected by auscultation .  Your veterinarian may hear muffled or displaced heart sounds.  Other signs include vomiting and difficulty in breathing.

Diagnosis is based upon physical exam, x-ray, and ultrasound.  Ultrasound is the most effective for diagnosis the effusion and for detecting pericardial and cardiac masses.

Treatment involves relieving the cardiac compression by removing the fluid with a needle placed into the sac. Surgery may be required.  The prognosis is based upon the underlying cause.

Heartworm disease- Refer to those articles also in the library.

Hypertension- Refer to those articles also in the library.

Thrombosis:

Thrombosis is a blood clot in a vessel obstructing blood flow.

The diagnosis is based upon clinical signs, index of suspicion, and use of a doppler to measure blood flow in certain situations.

Treatment includes removal or disintegration of the clot, controlling the underlying disorder, and supportive care to damage tissues.  The prognosis is poor.

Congenital heart diseases:

Congenital heart disease is the most common heart disease in animals less than one year of age.

The scope of this article is to list these diseases.  Please consult with your veterinarian or a veterinary cardiologist regarding these diseases.

These include patent ductus arteriosis, subvalvular stenosis, pulmonic stenosis, valvular dysplasia, atrial and ventral septal defects, and pericardial diaphragmatic hernias.

Signs include that of congestive heart failure.

Diagnosis is based on physical exam as a puppy or kitten.  Auscultation may reveal a murmur.  X-ray and ultrasound as well as angiocardiography (dye injection) are more definitive as to the type and severity of the disease

Treatment-

Referral to a cardiologist is the best course of treatment.

Arrhythmias (abnormal heart beats) are also diseases found in both cats and dogs and are beyond the scope of this article.

Thanks to Hill's Prescription Diets for the illustrations